Re: Limits of Kinds in Hawaii
David Campbell (bivalve@mailserv0.isis.unc.edu)
Wed, 19 Nov 1997 16:18:51 -0400The Hawaiian chain is forming as the Pacific plate passes over a "hot spot"
in the mantle, so new islands keep forming and old ones erode away. The
chain extends all the way back to near Siberia as underwater remnants, with
increasingly older rocks as one goes back. It's thought that some land has
been present for about 30 million years; any terrestrial organisms that
could "island hop" could have arrived in the Hawaiian chain as early as
that. Existing large islands are only a few million years old.
Even within a lineage, the rate of change in Hawaii has varied. The Nene,
a Hawaiian goose, is descended from the familiar mainland Canada Goose.
There also was a large, flightless goose wiped out by the Polynesians,
morphologically much more distinct from standard geese, yet it evolved more
recently than the Nene from the Canada Goose.
David Campbell